1. Field of the Invention
The present invention relates to a decoder and decoding method for decoding low-density parity-check codes with parity check matrices.
2. Description of the Related Art
Attention has recently been paid to low-density parity-check codes (LDPC codes) used as error detection and correction codes. Message-passing algorithms are known as a technique for decoding LDPC codes from, for example, Andrew J. Blanksby and Chris J. Howland, “A 690-mW 1-Gb/s 1024-b, Rate-½ Low-Density Parity-Check Code Decoder”, IEEE Journal of Solid-State Circuits, Vol. 37, No. 3, pp. 404-412, March 2002. In the message-passing algorithms, to decode LDPC codes, bit update computation, which is performed for each row of a check matrix (parity-check matrix), and parity update computation, which is performed for each column of the matrix, are iteratedly executed.
When decoding LDPC codes using the message-passing algorithms, bit update computation and parity update computation depend upon each other. Therefore, in the prior art, parity update computation of one loop cannot be started unless bit update computation of one loop is finished, and bit update computation of the next loop cannot be started unless parity update computation of the one loop is finished.